The present invention generally relates to a novel process for selective coupling of terminal olefins with ethylene to manufacture linear xcex1-olefins in the presence of organometallic coupling catalysts.
Linear xcex1-olefins are versatile intermediates and building blocks for the chemical industry. Their main applications are as comonomers for polyethylene (C4-C8), feedstock for surfactants (C12-C20), and plasticizers (C6-C10). Hydrocarboxylation of the C6-C8 xcex1-olefins with cobalt-carbonyl/pyridine catalysts gives predominantly linear carboxylic acids. The acids and their esters are used as additives for lubricants. The C6-C10 xcex1-olefins are hydroformylated to odd-numbered, linear primary alcohols, which are converted to surfactants or to polyvinyl chloride (PVC) plasticizers with phthalic anhydride. Oligomerization of (preferably) 1-decene using BF3 catalysts gives oligomers that are used as synthetic lubricants, which are known as poly-xcex1-olefins (PAO) or synthetic hydrocarbons. The C10-C12 xcex1-olefins can be epoxidized by peracids; this opens up a route to bifunctional derivatives or ethoxylates as nonionic surfactants.
xcex1-Olefins are produced worldwide at a rate of ca. 4xc3x97109 lb/year, predominantly through oligomerization of ethylene because of the high product quality and the good availability of ethylene. [Vogt, D. In Applied Homogeneous Catalysis with Organometallic Compounds; Cornils, B., Herrmann, W. A., Eds: VCH Publishers: 1996; Vol. 1: pp 245-256. (b) Parshall, G. W.; Ittel, S. D. In Homogeneous Catalysis: The Applications and Chemistry of Catalysis by Soluble Transition Metal Complexes; John Wiley and Sons: New York, 1992; pp 68-72. (c) Skupinska, J. Chem. Rev. 1991, 91, 613]. Current industrial commercial processes give xcex1-olefins with a Schulz-Flory distribution, wherein the S-F constant is calculated from the ratio Cn+2 to Cn compounds in the product mixture, also known as the chain growth factor (xcex1). Other routes to xcex1-olefins in decreasing importance are paraffin wax cracking, paraffin dehydrogenation, and alcohol dehydration.
The wide application and increasing need for xcex1-olefins, as comonomers for polyolefins will cause the linear olefin market to grow. Linear xcex1-olefins are very versatile intermediates and building blocks for the chemical industry. The lower C4-C8 xcex1-olefins are mainly used as comonomers for polyethylene. Small amounts of up to 3% xcex1-olefins are used to produce high-density polyethylene (HDPE) with a higher environmental stress/crack resistance and a slightly reduced density (0.959-0.938 g/cm3) compared with the homopolymer (0.965-0.955 g/cm3). Higher quantities of 4-12% xcex1-olefins are added to produce linear low density polyethylene (LLDPE) with considerably reduced density (0.935-0.915 g/cm3), for which 1-butene and 1-hexene are preferred in the gas-phase process and 1-octene in the liquid phase. [Vogt, D. Applied Homogeneous Catalysis with Organometallic Compounds. Cornils, B.; Herrmann, W. A. Eds. VCH Publications, New York. 1996, p. 220.]
Other applications for xcex1-olefins include feedstocks for surfactants (C12-C20) and plasticizers (C6-C10). Hydrocarboxylation of the C6-C8 xcex1-olefins with cobalt carbonyl/pyridine catalysts gives predominantly linear carboxylic acids. The acids and their esters are used as additives for lubricants. The C6-C10 xcex1-olefins are hydroformylated to odd-numbered linear primary alcohols, which are converted to polyvinyl chloride (PVC) plasticizers with phthalic anhydride. Oligomerization of (preferably) 1-decene, applying BF3 catalysts, gives oligomers used as synthetic lubricants known as poly-xcex1-olefins (PAO) or synthetic hydrocarbons. The C10-C12 xcex1-olefins can be epoxidized by peracids; this opens up a route to bifunctional derivatives or ethoxylates as nonionic surfactants. Two basic reactions are commercially used to produce xcex1-olefins. The first is based on the Aufbau reaction which oliogmerizes ethylene by the action of a trialkylaluminum. Two variations are practiced commercially. The first variation is a two-step process in which the chain-growth reaction is first accomplished at about 100xc2x0 C. and 10 MPa ethylene pressure. In the following high-temperature elimination step, the xcex1-olefins are displaced by ethylene at about 300xc2x0 C. and 1 MPa. In this stoichiometric reaction sequence, a Poisson distribution of xcex1-olefin products is obtained. The main disadvantage of this process is the large amount of aluminum alkyls needed in an industrial plant. To overcome this drawback, the following processes were developed.
An alternative process based on the Aufbau principle uses a one-step catalytic procedure, where chain growth and elimination occur simultaneously in the same reactor. About 0.4% wt. of AlEt3 (with respect to ethylene reacted) is needed. For this process solvent heptane is used, at about 200xc2x0 C. and 25 MPa ethylene pressure. After the reaction, the catalyst is destroyed by hydrolysis. In this catalytic reaction, a Schulz-Flory distribution of xcex1-olefin is obtained.
A variation of this second method is based on a combination of stoichiometric and catalytic chain-growth reactions. Unifying these two parts with a transalkylation step allows very efficient control of the xcex1-olefin chain lengths. The first oligomerization step uses a catalytic one-step process similar to the first process. The process is operated at 160-275xc2x0 C. and 13-27 MPa of ethylene pressure. After the reaction, the catalyst is destroyed by hydrolysis.
The product mixture, consisting mainly of C4-C10 xcex1-olefins, is distilled and separated into the C4-C10 and C12-C18 fractions. The latter can be used directly. The lower xcex1-olefins are subjected to transalkylation with higher aluminum alkyls, liberating the higher xcex1-olefins. The higher aluminum alkyls are produced in the stoichiometric part of the reaction, operating at about 100xc2x0 C. and 20 MPa. In the second distillation, the liberated olefins are separated from the aluminum alkyls. These alkyls are fed into a chain-growth reactor, where they are grown with ethylene to long-chain aluminum alkyls, which are recycled to the transalkylation stage. Because of the recycle, co-oligomerization of product xcex1-olefins with ethylene yields considerable amounts of branched olefins. The higher molecular weight C6-C18 fraction, especially, consists of only 63% linear xcex1-olefins. The problem associated with both of the aforementioned processes is that they are done under stoichoimetric conditions and exhibit very low yields of xcex1-olefins.
Another commercially available process is based upon the second basic reaction and produces poly-xcex1-olefins by the oligomerization of ethylene. This process is known as the Shell Higher Olefin Process (SHOP). Catalysts used in this process are neutral Ni(II) complexes bearing bidentate monoanionic ligands [(a) Peuckert, M.; Keim, W. Organometallics 1983, 2, 594. (b) Keim, W.; Behr, A.; Limbacker, B.; Kruger, C. Angew. Chem. Int. Ed. Engl. 1983, 22, 503. (c) Keim, W.; Behr. A.; Kraus, G. J. Organomet. Chem. 1983, 251, 377. (d) Peuckert, M.; Keim, W. J. Mol. Catal. 1984, 22, 289. (e) Keim, W.; Schulz, R. P. J. Mol. Catal. 1994, 92, 21]. This ethylene oligomerization process combines oligomerization of ethylene, isomerization of the higher xcex1-olefin products and the metathesis of these internal olefins with butenes or ethylene. It was designed to meet the market need for linear xcex1-olefins for detergents. The nickel catalyst is prepared in situ from a nickel salt, e.g., nickel chloride, and a chelating phosphorus oxygen ligand like o-diphenylphosphinobenzoic acid. The nickel catalyst oligomerizes ethylene in toluene at 80xc2x0 C. and 5 MPa to 99% linear olefins with 98% xcex1-olefins. The xcex1-olefins produced have a Schulz-Flory type of distribution over the whole range from C4-C30+.
Problems associated with the aforementioned ethylene oligomerization process are that ethylene is a very expensive feed material and that the resultant xcex1-olefins (i.e., C4-C30+) have to be fractionated to yield the desired carbon numbered linear xcex1-olefins. Another problem associated with such oligomerization is that undesirable branching and multiple isomeric olefins often result, thereby requiring a separate fractionation step which is both expensive and results in substantially lower selectivity yields of the desired linear xcex1-olefin.
The present inventors have unexpectantly discovered a novel catalytic process for selective xe2x80x9ccouplingxe2x80x9d of terminal olefins with ethylene to manufacture linear xcex1-olefins in high yields with respect to ethylene and selectivity without the need for fractionation as discussed above. The unique process according to the present invention permits the xe2x80x98designingxe2x80x99 of a single carbon number linear xcex1-olefin, while using, in part, less costly raw materials than expensive ethylene. This unique catalysis process can be used to make C6-C10 olefins by sequential coupling reactions using an xcex1-olefin and ethylene, provided that the xcex1-olefin is not ethylene, thereby avoiding the need to fractionate larger xcex1-olefins, as required in the ethylene oligomerization process.
The present invention also provides many additional advantages which shall become apparent as described below.
A unique catalytic process for selectively coupling xcex1-olefins (e.g., propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene) with ethylene, wherein the xcex1-olefins are used with ethylene so as to produce the desired linear C6-C10 xcex1-olefins in high yield. The catalytic process according to the present invention provides for a unique method for converting xcex1-olefins having a carbon number of, for example, Cn, to linear xcex1-olefins having a carbon number of Cn+2, wherein n is an integer from about 3 to about 20. For example, this process provides for the coupling of: 1-butene with ethylene to produce 1-hexene, or 1-hexene with ethylene to produce 1-octene, or 1-octene with ethylene to produce 1-decene. The present invention utilizes a unique organometallic catalyst that is capable of producing: (a) a Cn+2 linear xcex1-olefin from ethylene and a Cn xcex1-olefin; and/or (b) xcex1-olefin products wherein every product contains at least one Cn fragment stemming from a reactor Cn reactor feed.
In general, the process for producing a linear xcex1-olefin according to the present invention comprises: reacting a feed comprising a stoichiometric excess of a terminal Cn olefin with ethylene in the presence of an organometallic catalyst to produce a Cn+2 linear xcex1-olefin, wherein said catalyst is capable of producing a Schulz-Flory distribution of less than about 0.8 as observed for ethylene oligomerization and wherein n is an integer between about 3 to 20.
The terminal olefin is preferably selected from the group consisting of C3 to C20 olefins, e.g., propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene and mixtures thereof, such that the product linear xcex1-olefin is selected from the group consisting of: C5 to C22 linear xcex1-olefins, preferably C6-C10 linear xcex1-olefins. Preferably, a feed containing a mixture of three or less terminal olefins will be utilized, more preferably, a feed containing a single olefin will be utilized.
The coupling step is preferably conducted at a temperature in the range from about xe2x88x92100 to about 250xc2x0 C., more preferably between about room temperature to about 100xc2x0 C. The pressure during the coupling step is conducted at a pressure from about 0 to about 30,000 psig, preferably between about 0 to about 10,000 psig, most preferably between about 5 to about 3,000 psig.
The terminal olefin to ethylene typically has a molar ratio in the range between about 2:1 to about 1,000:1, preferably between about 10:1 to about 100:1.
The reaction step is preferably a catalytic coupling of said terminal olefin and said ethylene to form said linear xcex1-olefin. It is also preferred that the reaction step be performed in the presence of a solvent. The solvent is preferably at least one solvent selected from the group consisting of: ethane, propane, butane, pentane, hexane, toluene, cyclohexane, cyclopentane, tetralin, methylene chloride, chlorobenzene, chloroform, o-dichlorobenzene, carbon dioxide and mixtures thereof.
The catalyst is preferably a transition metal-based catalyst selected from the group consisting of: Group 6 metals, Group 8 metals, Group 9 metals, Group 10 metals, Group 11 metals (IUPAC) or mixtures thereof. The transition metal-based catalyst is typically at least one selected from the group consisting of: chromium trimerization catalysts, Brookhart type transition metal catalysts, iron or cobalt catalysts, pseudotetrahedral nickel complex catalysts, sulfur-containing nickel complexes and SHOP catalysts. The term xe2x80x9cpseudotetrahedralxe2x80x9d is used herein to describe the geometric structure of the metal complex, it does not exclude a pure xe2x80x9ctetrahedralxe2x80x9d geometrical arrangement. A more detailed description of pseudotetrahedral can be found in U.S. Pat. No. 6,180,788 herein incorporated by reference.
The process according to the present invention is either a continuous, semi-continuous or batch type process.
Finally, the linear Cn+2 xcex1-olefin of the present invention is formed from the reaction product of a stoichiometric excess of a terminal Cn olefin with ethylene in the presence of an organometallic catalyst.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawings, wherein like parts have been given like numbers.